While not as expensive as 087x numbers, 084x are still more expensive then calling land lines and those numbers are in the DB as well...
While there is already a large DB of UK numbers, there is relatively few 13/1300 numbers in the database and we encourage everyone that ever dialed a number to help locate geographical numbers, or email/phone companies asking for them.
Straight out asking doesn't always work, however you can put a spin on it like, I'm going overseas and I couldn't dial a 13 number when I was out of the country last time is there an alternative number I can try.
Failing that, we have setup a special forum thread
http://forum.e164.org/index.php?board=3.0 that people can post requests for numbers to.
If you want to manually lookup a number you can search via the main website, or via the e164 wap interface
http://wap.e164.org